This invention relates to cable wire fractures and fracture-tough wire produced from non-frangible aluminum (al) and titanium (ti) base alloys that transition from brittle to ductile metallurgical condition in processing. More specifically it relates to change in cable flaw state by eliminating wire fractures so as to increase reliability and service. Two (2) additional patent applications are submitted herewith, (1) Cable Stress and Fatigue Control Ser. No. 757,300, and (2) Deep Well Handling and Logging System, Ser. No. 757,552. These patent applications are related and copending.
It is found that alloys of al and ti have many attributes for use in cable tension members but two (2) attributes are common to selected alloys of each, and are crucial to this invention:
(1) High dynamic properties in the base metals including abnormally high spring which are essential to effective energy absorption, storage and dissipation in tension systems; and PA1 (2) Selected alloys are processed through brittle-ductile transition so as to embody high energy (in ft.-lbs) and fracture extension resistance, and then are non-frangible in cable structures. PA1 Simple bend stresses are .sigma.b=.delta./D.times.Ec with other bend stresses induced depending upon cable constructions PA1 Surface contact stresses are .sigma.c=K.sqroot.P PA1 Impact stresses are .sigma.i=Vo.sqroot.Ec.times..rho.c PA1 Internal stresses are local but may be generally severe as functions of relative mass density (.rho.c) and elasticity (Ec). PA1 1. Non frangible wires, having been processed through a brittle-ductile transition, then are assembled into work performing cable having a changed flaw state PA1 2. Compliant and ductile wires resist fracture and extension, and are permanently lubricated PA1 3. In service the wires have high resistance to wear, including abrasion, and strain-hardening, an uncommon set of attributes.
While selected steel alloys may likewise be non-frangible in test specimens they fail to qualify because of low dynamic properties and wire fractures, crucial to serviceability in steel work performing cable, and in the old manners, are extremely limiting in the use of effective design criteria for cable constructions.
In analyzing the significance of fractures in "work performing" cable, it should be recognized that the behavior of all structures is derived from both the type of mechanical force system and the metallurgical type of metal. The mechanical aspects involve the relative compliance characteristics which determine the stored energy available for fracture propagation (hereinafter called mechanical); the metallurgical aspects involve relative ductility characteristics which determine the energy absorption and dissipation capacity to fracture initiation and extension (hereinafter called metallurgical). These two (2) qualities of any structure operate in concert to determine how the structure will respond to loading in the presence of flaws, as has been commonly seen in the wire fractures and short service of steel cable. Essentially, the flaw state design of tension systems is the basis for assessment of these interactions as in any structure. In this context cable structures are complex, thus placing a premium on non-frangible, ductile wire to overcome structural flaws.
Characteristics cable stresses when performing work are:
These stresses are of course induced and superimposed upon cable tension. It may now be seen that frangible wire with low dynamic properties will not provide fracture-safe cable structures. Once wire fractures begin, as characteristic of structures having flaws, they continue and most often accelerate, wherein safety factors grow marginal until reaching a catastrophically low strength condition. In view of the complex construction of both axially symmetric and contrahelically wrapped electrochemical cable for sustaining primary loads and the characteristic severity of these dynamic stresses in performing work, three cable structures must be considered, (a) mechanically flawed (b) very sensitive to both mechanical and physical properties, and (c) metallurgical condition.